Relaying data packets over wireless channel within a multi-station cellular communication network, may be implemented between mobile stations (MSs) by utilizing multi-hop relaying. The cellular communication network typically employs Time Division Duplexing (TDD), and uses Code Division Multiple Access (CDMA) scheme for transmission and reception of control and user data over the air-interface.
Like user terminals, relays are not connected to the wire line network through a back haul connection, but rely on the wireless link with a base station BS. Relaying MSs or Mobile Station Relay (MSR) called hereafter, forward data received from the BS intended for another MS. MSR should be chosen such that its own traffic is not adversely impacted. Moreover, for efficient usage of network resources and load balancing, the MSR has to be selected carefully.
Using relays can help improve the performance for the users especially those at the edge of the cell or in shadowed areas in a cell. Use of relays in wireless networks also has many other advantages such as increased data rates, reduced interference due to reduction in transmission power, increased spatial reuse due to simultaneous transmission from both the relay and the BS.
The conventional relaying operation in cellular networks is performed via repeaters, which are used to extend the coverage to dead spots. Wireless repeaters provide e.g. radio frequency (RF) coverage to areas in a cell which either lack signal or, lack the required signal strength for adequate mobile phone performance. Insufficient coverage may occur and can include such areas as office buildings, parking garages, shopping malls, large convention halls, underground tunnels and freeways and residential homes Installing an active repeater system can solve the weak coverage problem. Repeater systems provide an effective solution by redirecting, filtering and amplifying the available signal at the donor antenna, into the weak coverage area, through a properly selected interior coverage antenna. This form of relaying is carried out in analog form, where the multi-hop signals are amplified and forwarded to the region to be covered.
Until now only bi-directional amplifiers have been used in second-generation cellular communication systems and will be introduced in third-generation cellular communication systems also. These analog amplifier type repeaters also increase the noise level (by amplifying the noise signals as well), which has limited their application in cellular communication systems.
Relaying can be performed in digital form also, in which case the relayer or repeater receives the multi-hop signal, demodulates and decodes it, and then re-encodes and re-modulates the signal before re-transmitting it to the relayed node or a Mobile Station Target (MST). The advantage of using digital relaying is that it is free of noise and interference.
Multi-hop wireless networking has been traditionally studied in the contest of ad hoc and peer-to-peer networks. While the goal of ad hoc networks is the ability to function without any infrastructure, the goal in the multi-hop wireless cellular communication networks is the almost ubiquitous provision of high data rate and coverage extension for cellular mobile communication systems.
Whenever relaying is performed, a relay node has to be selected which is required to receive the multi-hop signal from the BS, demodulate and decode that signal and re-modulate and re-encode the multi-hop signal before re-transmitting it to the relayed node. In the other direction, the selected relay node receives the multi-hop signal from the relayed node, demodulates and decodes that signal and re-modulates and re-encodes the multi-hop signal before re-transmitting it to the BS.
Routing is very critical and challenging in ad hoc networks since there is no central identity and the topology of ad hoc networks is very dynamic. However, decisions on routing or relay node selection in multi-hop augmented cellular communication systems can be facilitated by utilizing the centralized information available at the BS. Nevertheless, relay node selection is still quite critical in cellular communication systems, as the relay node selection strategy must meet various constraints such as various quality of service constraints, performance constraints and resource constraints.
Relay node selection using single criterion only may not select a good relay node in practical situations in which system objectives are multi-faceted. Multiple criteria are often needed in route selection since a single criterion cannot readily satisfy system performance metrics involving different applications. For example a delay sensitive application such as voice and video require high bandwidth whereas loss sensitive application such as Short Message Service (SMS) or Multimedia Message Service (MMS) require guaranteed delivery of data. Thus the criterion for relay route selection is different for different classes of applications. Furthermore, a single criterion based relay node selection scheme can severely compromise the network performance on the overlooked criterion. For example, a relay node selection scheme considering only path loss or physical distance between the intermediate hops and ignoring the remaining battery power at the relay node can lead to the rapid depletion of battery life of a nearby relay node.
Methods to select a relay node in devices having two air-interfaces which are cellular and ad-hoc respectively have been proposed, e.g. in US Patent Appl. No. US20040033778, B. Fonseca, J. D. Bonta, and G. Calcev. In such implementations, users access the cellular infrastructure through ad-hoc network capability whenever they cannot access the cellular network directly, or when they find it more advantageous to do so. The ad-hoc air-interface may for example be implemented utilising the BLUETOOTH standard. In such a method, the responsibility associated with relay node selection and allocation of wireless resources is moved from the direct cellular network air-interface to the additional, ad-hoc air-interface. Therefore, such relay node selection method hinge on the mobile units being capable of dual wireless access technologies, that is to cellular (direct) services, and ad-hoc services or BLUETOOTH network also.
It is with the knowledge of the above mention concerns that the present invention has been made and is now reduce to practice.